A direct tension test apparatus is typically used when the tensile mechanical property is measured for the brittle material such as the rock. FIG. 1 shows a supporter of a conventional tension test apparatus. When the tension test is performed by using this apparatus, the rigidity sleeve 4 can not support the weight of sample 8 and lower end cap 7 effectively. Therefore, when the force applied to the sample reaches a peak value, under the gravity effect on the sample, lower end cap and lower chain under the breaking plane, sudden breaking occurs to the sample, and the measurement of the material mechanical property after peak stress may not be performed. In order to solve such problem, the Chinese patent application No. 200610022224.8 discloses a technical solution which uses a support spring 8 to replace the rigidity sleeve 4 (shown in FIG. 2), in this way, throughout the tension test, the weight of sample 5 and other test components is supported by the spring 8 and the measurement of the whole process curve may substantially be completed. However, some new problems may be introduced by using this spring supporter and the problems mainly include: 1) the sample is broken at the end portion. Theoretically, breaking should occur in the middle of the sample. However, from the whole process of the tension test, during the tension process, the test data will be influenced due to the left and right sway of the spring and chain, which becomes more prominent especially during the test near the peak stress and after the peak value. In this case, the sample is broken at the end portion, which actually does not reflect the mechanical property of the brittle material during the whole tension process; 2) the applicability is poor. There is no corresponding stipulation on the sample size and specification of the direct tension test, so the volumes, weights, tensile strengths and so on of the samples may be considerably different, and thereby different support forces may be required for the supporters. For example, a spring with a larger stiffness coefficient may not be suitable for a small sample which is subject to tensile failure, otherwise it is the same as the rigidity supporter; on the contrary, a spring with a extremely small stiffness coefficient may not be suitable for a large sample which is not subject to tensile failure, otherwise the spring may be out of action. Therefore, many springs are required to be prepared for various samples, and there is a need for replacing the spring continuously when the tension tests are continuously performed for different samples, which increase the complexity of operation; 3) installation procedure is complex. As shown in FIG. 1, from the test process, when a test is completed and the next test is to be performed, the upper and lower bolts need to be taken down for replacing the sample, and then be mounted again. It can be seen from the figure, the lower joint, the lower bolt and the chain are enclosed by the spring. The space within the spring is strait and the interval between two rings is also small, which introduces inconveniences to the installation of the lower components; 4) distortion and aging may occur to the spring during the long time use, which may affect the performance of the spring. According to the above reasons, it is necessary to seek a supporter of the tension test apparatus which may overcome these drawbacks of the spring.